The effect of unsteady wake on the film cooling effectiveness of the turbine blade was studied using the pressure sensitive paint (PSP) measurement technique. The test blade had two rows of dust-pan shaped film holes on the suction surface and the pressure surface

respectively. The blowing ratio varied from 0.25 to 1.5 and the wake Strouhal number of 0

0.12

0.36. Results showed that as the wake Strouhal number increased

the span-wise averaged film cooling effectiveness of the suction surface decreased by up to 0.07 and the span-wise averaged film cooling effectiveness of the pressure surface decreased by up to 0.024. For the wake cases

an increase in the blowing ratio caused a decrease in film cooling effectiveness on the suction surface. The film cooling effectiveness increased first and then decreased on the pressure surface as the blowing ratio increased.